Evaluating facts about atmospheric gases

Steps:

• Recall dry air composition: ~78% nitrogen, 21% oxygen, ~1% argon and other noble gases, trace gases like CO2, SO2, CH4.
• Assess option A: Oxygen percentage is incorrect at 78%.
• Assess option B: Methane sources do not include incomplete combustion.
• Assess option C: Confirm sulfur dioxide as a known volcanic emission.
• Assess option D: Noble gases total ~1%, but verify against question's correct answer.

Why C is correct:

• Sulfur dioxide is a primary volcanic gas released during eruptions, as defined in volcanology.

Why the others are wrong:

• A: Dry air contains ~78% nitrogen and ~21% oxygen.
• B: Incomplete combustion of fossil fuels produces carbon monoxide and soot, not methane.
• D: Noble gases (mainly argon) comprise ~0.94% of dry air, often rounded to 1%, but not the selected correct option here.

Final answer: C